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Management of fit with soft contact to achieve optimal Anisometropic : vision and binocularity. Part-time occlusion therapy was also initiated, which was modified A Case Report and throughout the treatment period based on Brief Review clinical findings. She was also treated with Sung Hee (Kelly) Lee, OD, FAAO 19 sessions of office-based in order to maximize the success of amblyopia Graham B. Erickson, OD, FAAO, treatment. At the completion of the treatment, FCOVD this patient showed significant improvement in her and other non-acuity factors, including sensitivity and binocularity. ABSTRACT Background Conclusions

ARTICLE Unilateral functional amblyopia due The successful treatment of this patient with to is a common cause anisometropic amblyopia was achieved by of vision loss in children. There has been a the combination of active vision therapy with significant amount of research recently to evidence-based management strategies, determine the most effective management consisting of optical correction and occlusion strategies for such cases, and it is important therapy. for clinicians to determine how to apply these findings clinically. introduction Anisometropia is a common cause of Case Report functional amblyopia. It is often difficult to A 6-year-old female presented for her first detect without an effective vision screening or comprehensive exam after failing a school a comprehensive , as there are vision screening. She was diagnosed with typically no symptoms or obvious manifesting significant anisometropia with anisometropic signs. amblyopia in her left eye. She was treated with A generally accepted definition of aniso­ spectacle correction initially, and was eventually metropia is at least 1D difference of sphere or cylinder power between each eye.1,2,3,4 The Correspondence regarding this article should be potential amblyogenic amount of anisometropia emailed to Sung Hee (Kelly) Lee, OD, FAAO, at is suggested to be 1D for hyperopia, 3D [email protected]. All state­ments are the authors’ 5 personal opinions and may not reflect the opinions of for , and 1.5D for . The the College of Optometrists in Vision Development, reported incidence of amblyopia is 100% with Vision Development & Rehabilitation or any institution­ hyperopic anisometropia of 3.5D or higher, or organization to which the authors may be affiliated. Permission to use reprints of this article must be obtained and in myopic anisometropia of 6.5D or from the editor. Copyright 2019 College of Optometrists higher.1,2,6,7 in Vision Development. VDR is indexed in the Directory of Open Access Journals. Online access is available at In anisometropic amblyopia, visual depriv­ covd.org. https://doi.org/10.31707/VDR2019.5.2.p100 ation and the subsequent lack of adequate retinal stimulus are caused by optical defocus Lee SHK, Erickson GB. Management of anisometropic amblyopia: A case report and brief review. Vision Dev & and abnormal binocular inhibition in the Rehab 2019;5(2):100-12. more ametropic eye.1,3,6,8,9 In addition to acuity loss, these mechanisms also affect the normal development of other vision factors Keywords: Amblyopia; Anisometropia; including contrast sensitivity, , Vision Therapy oculomotor function, and eye-hand coordina­

100 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 tion.1,2,3,6,10 Another considerable factor is the no afferent pupillary defect in both . The compromised binocularity in these patients. confrontation visual fields were grossly full, Even after improvement of vision and deficient and extraocular muscle motilities were full vision skills in the amblyopic eye, and unrestricted in each eye. Cover testing and binocular inhibition patterns can remain as revealed ortho alignment at distance and obstacles for obtaining sensory fusion without 6Δ at near. No stereo acuity was further intervention. reported with the Lang I stereoacuity test. The In addition to recognizing the risk factors following are the results of objective : and clinical findings described above, the appropriate evidence-based management Dry Retinoscopy: strategies that should be considered for OD: +1.00D patients with anisometropic amblyopia include OS: +8.50-1.25x004 optical correction and occlusion. Further, active vision therapy (VT) should also be considered Wet Retinoscopy to potentially improve the efficacy and (1gtt 1% OU): facilitate the efficiency of the treatment. This OD: +2.00D case report demonstrates an effective course OS: +9.00-1.00x175 of treatment for anisometropic amblyopia using all of these strategies. Anterior and posterior segment ocular health were unremarkable. Case Based on the findings, AC was diagnosed AC, a 6-year-old female, presented for her with refractive amblyopia in the left eye first comprehensive eye exam after failing a secondary to high hyperopic anisometropia school vision screening. This first grader was of 6.5D (equivalent sphere). A spectacle told that her left eye was not “focusing” as correction was chosen over contact lenses since well as the right eye. Another optometrist protection of the sound eye was one of the at the clinic initiated the vision care of AC, treatment goals due to the severe amblyopia. before care was transferred to the authors. However, contact lenses to minimize anisei­ AC’s mother reported no noticeable problems konia were strongly recommended as a future regarding her eyes or vision and AC never option as the amblyopia resolves. A spectacle reported any complaints. AC’s health history prescription of +1.00D OD and +8.00- was unremarkable and the pregnancy and 1.00x175 OS was provided for full time wear. birth histories were normal. She was meeting The importance of compliance with spectacle normal developmental milestones and not wear was emphasized and she was advised to experiencing any difficulties at school. She return to the clinic in 6 weeks for a follow-up reported an to penicillin that causes evaluation of her prescription and amblyopia. a rash, and was taking no medication other than a multivitamin supplement. There was no Follow-Up Visit #1 known family history of any ocular conditions. AC’s mother reported good compliance with spectacle wear. The corrected distance Initial Exam visual acuities were 20/20 (1.0MAR) OD and AC’s uncorrected vision in the right eye 20/125- (6.3-MAR) OS with isolated single line was 20/20 (1.0MAR) at both distance and near; Snellen acuity. She demonstrated 400 arc however, the left eye was 20/250- (12.5-MAR) seconds of local stereo acuity with Wirt-type at distance and 20/200- (10.0-MAR) at near. circles on the Randot steroacuity test. The The were equally reactive to with over-retinoscopy findings through the current

101 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 spectacles revealed +1.25D OD and +0.25- with the Snellen single line, 20/50 (2.0MAR) 0.25x180 OS. The prescription was not modified with single letter, and 20/60- (3.0- MAR) with at this time, and it was decided to monitor. crowded Lea symbols. She reported no global AC’s optometrists at this visit initiated 2 hours stereo with the Randot butterfly stereoacuity of daily patching of the right eye with a Patch- test and 100 arc seconds of local stereo with works eye patch to expedite the recovery of the animals on the Randot test. The 3-Figure visual acuity. AC was recommended to engage Worth test revealed of the left eye in eye-hand coordination activities at near at distances farther than 1 meter. Visuoscopy while patching. A follow-up appointment was testing showed steady central fixation in the scheduled in 1 month. right eye and unsteady central fixation in the left eye. The clinical findings measured at Follow-Up Visit #2 this visit are summarized in Table 2. AC was AC still reported good compliance with recommended to attempt increasing patching spectacle wear. However, patching was to 2 hours a day while engaging in near eye- reported to be extremely difficult, and it could hand activities. The option of a contact only be done for about 30 minutes each day. correction was discussed again. AC’s mother The corrected distance visual acuity in the left was informed about the option of active vision eye improved to 20/80- (4.0-MAR) with Snellen therapy to potentially increase the efficacy of single line and 20/70 (3.5MAR) with Snellen occlusion therapy, decrease the treatment isolated letter. Over-retinoscopy results were duration, train the vision skill deficits in the consistent with the first follow-up visit, so the amblyopic eye, and maximize binocularity. right eye’s prescription was updated to +2.00D After the discussion, it was decided to pursue from +1.00D. The left eye’s prescription a correction and initiate a weekly remained unchanged. She was recommended vision therapy program. to try patching the right eye for 2 hours/ day, 7 days/week, and was educated on the Active Vision Therapy Program (28 weeks) importance of compliance with occlusion Active Vision Therapy therapy for maximum benefit. The next follow- Weekly 45-minute in-office vision therapy up visit was scheduled in 1 month. sessions were conducted, and AC’s visual acuity in her left eye was measured at Follow-Up Visits #3-5 each visit. In addition to daily patching, These follow-up visits were conducted in approximately 35 minutes of home therapy monthly intervals. AC had difficulty and poor was prescribed for 5 days each week. The compliance with the patching regimen of 2 compliance with in-office visits was good, with hours per day that was prescribed. For follow- moderate compliance with the prescribed up visits #3 and #4, minimal improvement home therapy activities. Progress evaluations of the VA in the left eye was measured. The were conducted every 4 to 5 visits to measure lack of further improvement was judged to be non-acuity factors. AC followed the general due to poor compliance with patching, and therapy sequence of monocular, bi-ocular, and therefore the prescribed patching regimen then binocular procedures. The monocular remained the same. phase activities included both accommodation Starting at follow-up visit #5, her care was and oculomotor activities. Although these transferred to the authors. By this point, she skills were not evaluated pre-vision therapy, was able to increase patching to 1 hour per they were assumed to be reduced due to the day for a few days a week. Corrected distance significant visual acuity reduction in the left visual acuity in the left eye was 20/60- (3.0- MAR) eye. Monocular phase was combined with the

102 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 bi-ocular activities, also known as monocular was given the spherical equivalent prescription fixation in binocular field (MFBF), to minimize in the amblyopic eye rather than a , the suppression of the amblyopic eye. When since the benefit of minimizing the fitting AC’s visual acuity in the amblyopic eye reached complications was determined to be more about 20/40 (2.0MAR) to 20/50 (2.5MAR), the beneficial than the optical improvement binocular therapy activities were initiated. An obtained by correcting 1D of with-the-rule emphasis was made on divergence activities astigmatism. The contact lens prescription as AC was showing relative difficulty compared of +2.00D OD and +8.00D OS was finalized. to convergence. The in-office and home Throughout AC’s follow-up visits and active activities included in her therapy program are vision therapy sessions, her prescription was listed below: closely monitored for any need of modification. 1. Monocular Phase: Majority of activities Cycloplegic were repeated when at the beginning of VT indicated, and her contact lens prescription a. Accommodation: Monocular was modified twice. The first modification Accommodative Rock was made shortly after AC’s initial contact b. Oculomotor: Hart chart , lens fit. A cycloplegic refraction result of rotating pegboard, symbol tracking +4.25-0.25x090 OD and +9.50-1.00x180 OS (modification of Michigan Letter confirmed the consistent over-refraction results Tracking) of +2.50D through the current prescription in the right eye. While the prescription in 2. Bi-ocular Phase: Activities done with the left (amblyopic) eye remained the same, red/green anaglyphic the right eye’s prescription was changed a. Sherman playing cards to +3.00D in both spectacles and contact b. Red mazes lenses. This modified prescription achieved c. Red symbol tracking symmetrical under-correction of hyperopia of approximately 1.25D in both eyes. The second 3. Binocular Phase: Initiated when VA of modification was made based on a repeatedly amblyopic eye reached 20/40-20/50 measured excessive lag of accommodation on a. Accommodation: Binocular MEM retinoscopy in both eyes. The amount Accommodative Rock of hyperopia compensation was increased in b. Vergence: Brewster-type both eyes to normalize the accommodative Stereoscope, Vectograms, VTS- response at near. At this visit, the contact lens 3 (multiple choice vergence with prescription was adjusted to +3.75 in the right random dot stereo targets) eye and +9.50 in the left eye, which resulted in +0.50D of uncorrected hyperopia in each eye After completion of the office-based through the prescription. Due to the left eye’s vision therapy program, maintenance therapy higher prescription and the limited availability with the Home Therapy System (HTS) was in the initial daily contact lens design chosen, prescribed for fusional vergence activities. the modality was changed to a monthly lens, and an appropriate cleaning regimen was Modification of Refractive Correction and recommended. Since AC was primarily wearing Patching Regimen During Active Vision her contact lenses, the spectacle prescription Therapy Program was not changed at this time; however, a copy By the second vision therapy session, AC of the updated prescription was released for was fit with daily modality contact lenses based future use. The history of prescription changes on her most recent spectacle prescription. She are summarized in table 1.

103 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 Table 1. Prescription (Rx) change history option of tapering or increasing the patching Wet Refraction regimen, AC’s mother agreed to increase it to a Initial OD: +2.00DS OS: +9.00-1.00x175 6 hours/day regimen. To maximize compliance, Assessment Rx (spectacles) the Patch-works patch was replaced with an OD: +1.00D OS: +8.00-1.00x175 adhesive patch; the parents were informed of Rx (spectacles) Rx change #1 possible adverse effects of skin irritation from OD: +2.00D OS: +8.00-1.00x175 the adhesive. With this new type of patch, AC Contact Lens Rx (CL) showed excellent compliance for the 6 hours/ (CL) fitting OD: +2.00D OS: +8.00DS day patching regimen. Wet Refraction OD: +4.25-0.25x090 OS: +9.50-1.00x180 Progress Evaluation Results and Further Rx (spectacles) Rx change #2 Treatment Plan OD: +3.00D OS: +8.00-1.00x175 After the completion of 19 sessions of Rx (CL) office-based vision therapy with occlusion OD: +3.00D OS: +8.00D therapy, a progress evaluation was conducted Rx (CL) Rx change #3 to obtain detailed measurements. AC’s OD: +3.75D OS: +9.50D corrected visual acuity in the right eye was Since the initiation of active vision therapy, 20/15 at distance and 0.32M at 40 cm. In the AC’s compliance with patching improved left eye, it was measured 20/30+1 (1.5+1MAR) and she was able to tolerate a 2 hours/day with Snellen single line, 20/30+ (1.5+MAR) with regimen for an average of 4 days each week. Snellen isolated letter, and 20/35 (1.8MAR) with By the 12th VT session, AC’s visual acuity in Wesson Psychometic acuity cards at distance. the amblyopic eye stabilized at 20/40 for Near VA in the same eye was 0.63M+ at 40cm. approximately 2 months. After discussing the AC was no longer reporting suppression OS

Table 2. Comparison of clinical measurements between initial visit, pre-VT visit, and post-VT visit. Test Initial (sc) Pre-VT (spectacle) Post-VT (contact lens) Distance VA (Snellen) OD: 20/20 OD: 20/20 OD: 20/15 OS: 20/250- (single line) OS: 20/60 (single line) OS: 20/30 (single line) 20/50 (single letter) 20/30 (single letter) Near VA (Lea) OD: 20/20 OD: 20/16 OS: <20/200 OS: 20/30- Psychometric VA OS: 20/35 (Wesson VA card) Stereoacuity* None reported (-) Global, 100” local (+) Global, 50” local OS suppression >3ft Distance: Ortho Distance: Ortho Distance: Ortho Near: 6 Exophoria Near: Ortho Near: Ortho Contrast Sensitivity (threshold) OD: 8% (@ 20/20) OD: 3.2% (@ 20/20) OS: 20% (@ 20/50) OS: 6.3% (@ 20/40) MEM OD: Variable large lag OD: +0.50D OS: Variable large lag OS: +0.50 D Near Vergence Range PFV: Unreliable PFV: X/8/X** NFV: Unreliable NFV: X/6/X ** * Lang I stereo test used at initial visit. Randot Butterfly and Wirt Circles stereo test used at subsequent visits. Child Worth test used for suppression test. ** Suppression at the break point.

104 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 Figure 2: Change of visual acuity (logMAR) in amblyopic eye throughout treatment and was able to see global stereo with the visits was initiated. For the home therapy, Randot butterfly and improved local stereo was the Computerized Home Therapy System measured with Wirt circles. Contrast sensitivity (HTS) was dispensed, and specific vergence measured with each eye’s threshold VA also activities were prescribed. AC’s performance improved in both eyes and MEM retinoscopy was monitored weekly using the software’s normalized. The suppression point for positive monitoring system and the prescribed activities fusional vergence (PFV) and negative fusional were modified accordingly. For accommodation vergence (NFV) were both reduced compared therapy, Binocular Accommodative Rock with to expected values. However, a discrepancy +/-2.50 lens flipper was prescribed. was noted on AC’s performance on the VTS-3 During her first 5 monthly follow-up visits, multiple choice vergence activity with random AC showed no regression in any clinical dot stereo targets, which showed a maximum measurement and her local stereoacuity of 27Δ for PFV and 12Δ for NFV. A comparison further improved to 40 seconds of arc. Her of the clinical measurements is shown in Table PFV performance on the VTS-3 system also 2, and the changes in visual acuity are shown improved; however, NFV remained unchanged. in Figure 2. The patching regimen was tapered further After this evaluation, the results were down to 1 hour a day for 3 days a week, then discussed with AC and her mother. As her to 1 day a week, and was eventually stopped visual acuity in the amblyopic eye stabilized as her findings, including VA, were stable. at 20/30 (1.5MAR) for approximately 2 months The Binocular Accommodative Rock and and her binocularity improved significantly, HTS program with emphasis on divergence the patching regimen was tapered down to 2 were continued for maintenance therapy. The hours a day. Also, the weekly vision therapy activities were eventually tapered down to 1 was discontinued and a maintenance home day a week based on her stable performance. therapy program with monthly follow-up She was followed periodically at the clinic even

105 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 Figure 1: Treatment timeline after the author moved to another location. She was eventually switched to a soft toric The potential amblyogenic amount varies lens in the left eye, which maintained 20/30+ depending on the type of refractive error. to 20/30-visual acuity. The most recent record, When assessing refractive error, objective which was 4 years following discontinuation measurement with retinoscopy is extremely of patching and active vision therapy, showed valuable since the central visual acuity in an that her vision stabilized at 20/40. amblyopic eye is unreliable for performing a subjective refraction.1,2,11 It is recommended Discussion to fully correct the amount of anisometropia, There has been a significant amount of and a cycloplegic refraction should be research conducted to determine the most completed to determine accurate values.1,12 effective treatment options for anisometropic When prescribing for patients with hyperopia amblyopia since it is a common cause of the Pediatric Investigator Group vision reduction in children. Recent research (PEDIG) guidelines require symmetrical under provides useful clinical guidance regarding correction of hyperopia up to 1.5D.12 When vision assessment, refractive error correction, prescribing for anisometropia, aniseikonia and and patching regimens to assist eye care its related symptoms must be considered.1,2,13-6 providers in managing this condition most A clinical rule-of-thumb is that 1D of effectively. In the case presented, patching, anisometropia causes about 1% aniseikonia contact lens wear, and active vision therapy when correcting with traditional spectacle were prescribed simultaneously in an attempt lenses. Patients with 2 to 3% of aniseikonia to achieve the maximum treatment results. often become symptomatic, experiencing Therefore, it should be noted that it is difficult symptoms such as reduction of stereoacuity, to determine how much each treatment alone , asthenopia, and/or contributed to AC’s visual acuity improvement. difficulties.17 However, when aniseikonia is AC’s treatment timeline is illustrated in Figure greater than 5 to 6%, no symptoms may be 1, and her change of visual acuity over the noticed due to suppression of an eye.18,19,20 course of treatment is shown in Figure 2. For symptomatic and potentially symptomatic patients, correction with contact lenses is a good option because it reduces aniseikonia

106 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 and can improve . Conventionally, to prescribe an appropriate regimen; and it was believed that aniseikonia is reduced 3) Which occlusion method is best for this most effectively by contact lenses in refractive individual. anisometropia, and by spectacles in axial Studies have shown that optical correction anisometropia. However, more recent studies alone can achieve significant improvement have found that contact lenses are more in amblyopia without any other intervention. effective in reducing aniseikonia than spectacles According to PEDIG study results, more than even in axial anisometropia.15,16 Therefore, a quarter of ATS patients with anisometropic contact lens correction is recommended in amblyopia showed resolution of amblyopia anisometropia greater than 2.5D-3D.1,2,6,8,15 with refractive compensation alone (greater In addition, contact lens correction does not than 20/30 in amblyopic eye, or less than 1 cause prismatic imbalance between each line of interocular difference). Furthermore, eye in different gaze positions that occurs in the subjects experienced stabilized acuity spectacle correction of anisometropia.14,20,21 with an average of 3-lines improvement Further, contact lenses improve cosmesis, with approximately 3 to 4 months of convenience for prescription modification, and optical correction wear alone.12 Based on compliance with prescription wear, especially this evidence, the full time use of optical when the sound eye requires a minimal correction may be initiated without occlusion, correction.1 Given all these advantages, and progression can be monitored for the first contact lens wear was recommended in this 4 months. This clinical application may allow particular case with a large anisometropia of avoidance of unnecessary occlusion therapy or 6.5D and suspected aniseikonia. However, in minimize the amount of occlusion time when any case where contact lenses are prescribed it is indicated.8,12 For the patient discussed in for amblyopic patients, the patient should this case, occlusion was initiated at the same be counseled on the potential for contact time when the glasses were prescribed. We lenses complications in the sound eye, since speculate that the visual acuity improvement the risk of vision loss is higher in this patient noted in the early phase of the treatment is group.22 In severe amblyopia, spectacles with mainly a result of the refractive error correction impact resistant lenses are a prudent option alone since her occlusion therapy compliance to provide protection for the sound eye; this was very limited. The overall period of occlusion can also be combined with contact lens wear. therapy would likely have been reduced if it was initiated after the visual acuity stabilized Occlusion Therapy with full time wear of the optical correction Occlusion of the sound eye has been first, which can be a significant benefit for the treatment of choice for amblyopia, and both the patient and her parents. recent research, including PEDIG Amblyopia When occlusion therapy is necessary Treatment Studies (ATS), has provided useful to obtain further acuity improvement in information regarding effectiveness of various amblyopia, an effective patching regimen amblyopia treatment options. Since occlusion depends on the baseline acuity in the treatment can be a significant burden for both amblyopic eye. An ATS study found that, when patient and caregiver,4,23 it is important to combined with near activities, daily patching consider how to achieve the maximum effect of 2 hours/day is as effective as 6 hours of with the minimal amount of treatment time. For patching for moderate amblyopia with acuity this purpose, the following questions should between 20/40 and 20/10024, and 6 hours/day be considered before initiating occlusion is as effective as full time patching for severe therapy: 1) When to initiate occlusion; 2) How amblyopia with acuity worse than 20/100.25

107 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 Furthermore, a recent study suggested that it supporting this strategy only applies to total is reasonable to initiate a 2 hours/day regimen occlusion with an adhesive patch. even with severe amblyopes, and increase it According to a long term follow-up to 6 hours/day if improvement plateaus.26 As study, the majority of patients with moderate seen in AC’s case, some patients experience amblyopia who were treated with either difficulty complying with patching despite patching or at 7 years of age or a variety of methods available, including younger maintained their acuity improvement adhesive, pirate, or a spectacle frame-attached at 15 years of age.30 Despite this finding, patch. For these patients, partial occlusion cessation of patching therapy should still options can be considered as alternatives be administered with caution to further to patching. A graded Bangerter foil, a film minimize the recurrence of amblyopia once that is applied to the lens of spectacles to the maximum improvement is achieved. The achieve reduced acuity in the sound eye, definition PEDIG used for recurrence is “2 or was also found to be an effective treatment more logMAR levels reduction in 2 consecutive choice for moderate amblyopia.27 Although measures.”31 The risk of recurrence in children the study could not conclude its treatment who have undergone occlusion therapy before effectiveness relative to patching, Bangerter the age of 12 was found to be low (7%) to foil use was found to have less treatment moderate (24%), depending on the type and burden.27 Another option for partial occlusion duration of treatment.31,32 This recurrence rate therapy is atropine penalization. According to was determined to be minimized by tapering a randomized clinical trial, 1% atropine therapy rather than abruptly stopping occlusion for was found to be as effective as patching in patients treated with 6 or more hours of daily moderate amblyopia.23 Further study also patching.33 Therefore, patients with associated showed that weekend and daily atropine led risk factors, such as good visual acuity (≥ 20/32) to similar visual acuity outcomes.28 Studies at cessation, larger improvement of acuity that compared patching with an adhesive during the treatment, or previous history of patch to atropine penalization showed better recurrence should be monitored with extra compliance, easier administration, and better caution.31,33 cost effectiveness with atropine.23 However, There has been recent interest in deter­ atropine can cause photosensitivity, allergic mining the effectiveness of using binocular reaction (rarely), and poor cosmesis in light computer/tablet games alone as a new colored irides.23 More importantly, atropine treatment option for amblyopia. Some studies penalization interferes with binocularity since it showed that a binocular game alone was not as impairs accommodation in the penalized eye. effective as part-time patching in improvement Once the specific occlusion method for of visual acuity and stereoacuity,34-36 whereas the individual patient has been selected, the others showed promising results with clinically amblyopic eye should be closely monitored. significant improvement in visual acuity and/or When there is no improvement of visual acuity stereoacuity, as well as the compliance of the for about 2-3 months, a clinical judgment treatment.37-44 The PEDIG randomized clinical has to be made to either modify the current trials with 5- to 12-year-olds and 13- to 16-year regimen or to cease the treatment. When the olds comparing binocular iPad games to part patient is motivated and compliant, increasing time patching found fairly poor compliance the occlusion regimen should be considered with the binocular iPad games; only 22.2% since it was found to be effective in achieving and 13% completed more than 75% of the additional improvement when there is prescribed treatment, respectively.34,35 Use of residual amblyopia.29 However, the evidence flicker glasses that provide rapid alternating

108 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 occlusion is another new approach to treat in anisometropic amblyopia. Due to the amblyopia.45 This device provides rapid relative optical defocus in one eye, binocular square-wave alternation of visual stimuli to inhibition can cause suppression or reduction help break suppression.45 These encouraging in stereoacuity as a result.1-3,6-9,48 Despite new treatment options should be studied with having equal visual acuity, it was found that further research, as they may be beneficial patients with a history of successful occlusion particularly in cases where occlusion therapy treatment for anisometropic amblyopia may not be practical. However, until their can still show reduced stereoacuity when effectiveness is clearly proven, occlusion compared to an age-matched population therapy should remain an integral part of without the condition.49 According to many amblyopia treatment. studies, reduction in stereoacuity is associated more with the amount of anisometropia Non-Acuity Factors of Amblyopia rather than the interocular difference in visual While many clinicians use visual acuity as acuity.7,8,13,16,49 Also, it was found that patients the sole outcome measurement when treating with hyperopic anisometropia are more affected amblyopia, it must be recognized that the by the amount of anisometropia, and likely to amblyopic eye has additional visual deficits. have greater reduction in stereopsis compared The crowding effect is a well-known and to those with myopic anisometropia.16 As characteristic deficit of amblyopia. Therefore, mentioned previously, contact lenses are often the current evidence-based methods of the best method for correcting anisometropia acuity assessment, including ATS-HOTV and to improve binocularity.1,2,8,16,20 Early Treatment Diabetic Study (ETDRS) protocol with single-surrounded Vision Therapy ototype, are recommended to obtain the Although there has yet to be a large- most accurate and consistent measurements. scale randomized clinical trial supporting When these methods are unavailable, the vision therapy for amblyopia treatment, vision psychometric visual acuity method can be therapy is often recommended concurrently used as it has the least variability, which is with occlusion therapy to improve treatment helpful since fluctuations in measurements are efficacy and reduce treatment time.50-54 often evident in amblyopia.1,2,11,46 Contrast Further, it is typically designed to address sensitivity can be another measure to monitor the non-acuity deficits in the amblyopic with amblyopia, as its improvement can eye, thereby maximizing visual function achieve visual function gain without change in and binocularity.1,2,3,17,46 The vision therapy visual acuity.1,2,17,46 Those with anisometropic activities can be categorized into three phases: amblyopia typically have reduced contrast monocular, bi-ocular, and binocular.2,8,17,46 sensitivity in all spatial frequencies compared Monocular activities can be prescribed to to strabismic amblyopia where there is often enhance accommodation, pursuit and saccadic only a reduction at high spatial frequencies.46-7 eye movements, and eye-hand coordination In addition, there are often deficits in with the amblyopic eye, and can be done accommodative and saccadic function in the while patching or with atropine penalization. amblyopic eye, as it has not received the same Bi-ocular, also known as monocular fixation level of visual stimulation as the sound eye.18,46 in binocular field (MFBF), activities allow only Eye-hand coordination deficits are another the amblyopic eye to see stimulus details consideration due to diminished spatial while both eyes receive peripheral stimuli judgment from reduced binocularity.1,2,6,17,18,46 using anaglyphic filters.1,6,48 The amblyopic Abnormal binocularity is an important deficit eye typically sees red colored central targets

109 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 through the green filter while the sound eye a better acuity outcome.1,8,20,49 In addition, only gets peripheral information through some studies found the presence and degree the red filter due to filter cancellation. The of pre-treatment stereoacuity are associated activities with red targets, such as mazes, with better post-treatment stereoacuity, as symbol tracking, and playing cards, can be well as visual acuity in the amblyopic eye.8,49 used during this phase. It is a good transition Historically, there has been some controversy from the monocular to binocular phase as it over age-related limitation to treatment minimizes the inhibitory effects that occur in success for amblyopia.59-61 However, it was anisometropic amblyopia.1,2,6,48 When visual shown that older children (ages 13 to 17 years) acuity of the amblyopic eye improves to could also obtain a significant improvement approximately 20/40 (2.0MAR) and suppression from compliant occlusion therapy, especially is reasonably controlled with MFBF, binocular if they had not been treated previously.57,62 A activities can be initiated to achieve maximum possible contributing factor in older children sensory and motor fusion ability. Treatment was that their treatment compliance is often with atropine penalization interferes with worse when compared to younger children.20 this phase, as accommodation in both eyes is required for successful binocular therapy. Conclusion Commonly used activities include tranaglyphs, This case report demonstrates how aniso­ vectograms, stereoscopes, and binocular metropic amblyopia was effectively managed accommodation procedures. In addition, there by the discussed treatment strategies, are numerous computer software programs consist­ing of optical correction and occlusion that allow for binocular training with anaglyphic therapy, supported by recent research. A or LCD shutters. In addition to improvement program of vision therapy was incorporated of stereopsis, the sensorimotor fusion training into the treatment to address specific visual may also improve the efficacy of treatment for deficits and potentially increase the efficacy mild residual acuity loss that is often harder to of the treatment. Additional improvement was obtain.1,2 achieved by increasing the patching regimen when visual acuity stabilized at a sub-par level; Prognosis of Anisometropic the regimen was then tapered to minimize Amblyopia Treatment the chance of recurrence of amblyopia. The Generally, a successful outcome of ambly­ non-acuity vision deficits related to amblyopia opia treatment is considered to be visual were addressed and improved by active vision acuity better than 20/30 (1.5MAR) in the therapy, and the patient’s binocularity was amblyopic eye, or less than 1 line of intraocular further maximized with contact lens wear. The difference.12,23-5,27-29,31,46,49,55-57 Good compliance combination of these treatments was used with optical correction use and occlusion are the as the best attempt to maximize results in most important prognostic factors for amblyopia managing this case. therapy.1,3,23,58 The use of optical correction is particularly important in anisometropic References amblyopia since it is critical for the amblyopic 1. Caloroso EE, Rouse MW. Clinical Management of eye to receive the clearest retinal image for . Santa Ana: Optometric Extension Program Foundation, 2007:17-22, 113-125, 175-199. https://doi. improvement. Another positive prognostic org/10.1177/026461969301100310 factor is commencing treatment with better 2. Griffin JR, and Borsting, EJ. Binocular Anomalies: Therapy, initial visual acuity. Since there is a correlation Testing & Therapy. Volume 2. 5th Edition. Santa Ana: with amount of anisometropia, patients with Optometric Extension Program Foundation, 2010:126-146. less anisometropia can be predicted to have

110 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 3. Rouse MW. Optometric clinical practice guideline: care 20. Sen DK. Results of treatment of anisohypermetropic of the patient with amblyopia. American Optometric amblyopia without strabismus. Br J Ophthalmol 66 Association, 1994. Web. 26 Jan. 2014. (1982):680-684. https://doi.org/10.1136/bjo.66.10.680 4. Summers CG., et al. Preferred Practice Pattern: Amblyopia. 21. Oguchi, Y, Mashima, Y. The influence of aniseikonia on American Academy of 2012. Web. 10 Feb. the VEP by random-dot stereogram. Acta Ophthalmol 67 2014. (1989):127–130. 5. Varma R., et al. The multi-ethnic pediatric eye disease 22. Tommila V, Takkanen A. Incidence of loss of vision in the study: design and methods. Ophthalmic Epidemiol. 13 health eye in amblyopia. Br J Ophthalmol 65 (1981)575-7. (2006):253-62. https://doi.org/10.1080/09286580600719055 https://doi.org/10.1136/bjo.65.8.575 6. Ciuffreda KJ, Levi DM, Selenow A. Amblyopia: Basic 23. Pediatric Eye Disease Investigator Group. A randomized Clinical Aspects. Stoneham: Betterworth-Heinemann, trial of atropine vs. patching for treatment of moderate 1991. amblyopia in children. Arch Ophthalmol 120 (2002):268- 7. Weakley DR. The association between nonstrabismic 278. https://doi.org/10.1001/archopht.120.3.268 ani­so­metropia, amblyopia, and subnormal binocularity. 24. Pediatric Eye Disease Investigator Group. A randomized Ophthal­mology 108 (2001):163-171. https://doi.org/10.1016/ trial of patching regimens for treatment of moderate s0161-6420(00)00425-5 amblyopia in children. Arch Ophthalmol 121 (2003):603- 8. Caputo R., et al. Factors influencing severity of and 611. https://doi.org/10.1001/archopht.121.5.603 recovery from anisometropic amblyopia. Strabismus 15 25. Pediatric Eye Disease Investigator Group. A randomized (2007):209-14. https://doi.org/10.1080/09273970701669983 trial of prescribed patching regimens for treatment 9. Von Noorden GK. Amblyopia: a multidisciplinary approach. of severe amblyopia in children. Ophthalmology 110 Invest Ophthalmol Vis Sci 26 (1985):1704-16. (2003):2075-2087. https://doi.org/10.1016/j.ophtha.2003.08.001 10. Von Noorden GK. Factors involved in the production 26. Wallace DK, et al. Time course and predictors of amblyopia improvement with 2 hours of daily patching. of amblyopia. Brit J Ophth 58 (1974):158-164. https://doi. JAMA Ophthalmol 133 (2015):606-9. org/10.1136/bjo.58.3.158 https://doi.org/10.1001/ jamaophthalmol.2015.6 11. Davidson DW, Eskridge JB. Reliability of visual acuity measures of amblyopic eyes. Am J Optom Physiol 27. Pediatric Eye Disease Investigator Group. A randomized trial comparing Bangerter filters and patching for 54 (1977):756-66. https://doi.org/10.1097/00006324-197711000- the treatment of moderate amblyopia in children. 00003 Ophthalmology 117 (2010):998-1004. https://doi.org/10.1016/j. 12. Pediatric Eye Disease Investigator Group. Treatment ophtha.2009.10.014 of anisometropic amblyopia in children with refractive 28. Pediatric Eye Disease Investigator Group. A randomized correction. Ophthalmology 113 (2006):895-903. https://doi. trial of atropine regimens for treatment of moderate org/10.1016/j.ophtha.2006.01.068 amblyopia in children. Ophthalmology 11 (2004):2076- 13. Dobson V, et al. Associations between anisometropia, 2085. https://doi.org/10.1016/j.ophtha.2004.04.032 amblyopia, and reduced stereoacuity in a school-aged population with a high prevalence of astigmatism. Invest 29. Pediatric Eye Disease Investigator Group. A randomized trial of increasing patching for amblyopia. Ophthalmology. Ophthalmol Vis Sci 49 (2008):4427–36. https://doi.org/10.1167/ 120 (2013):2270-2277. iovs.08-1985 14. Edwards KH. The management of ametropic and 30. Repka MX, et al. Atropine vs patching for treatment anisometropic amblyopia with contact lenses. Ophthal of moderate amblyopia follow-up at 15 years of age 19 (1979):925-929. of a randomized clinical trial. JAMA Ophthalmol 132 (2014):799-805. https://doi.org/10.1001/jamaophthalmol.2014.392 15. Rose L, Levinson A. Anisometropia and aniseikonia. 31. Pediatric Eye Disease Investigator Group. Risk of amblyopia Am J Optom Physio Opt 49 (1972):480-4. https://doi. recurrence after cessation of treatment. J AAPOS 8 org/10.1097/00006324-197206000-00003 (2004):420-428. https://doi.org/10.1016/s1091-8531(04)00161-2 16. Winn B., et al. The superiority of contact lenses in the correction of all anisometropia. Journal of British Contact 32. Pediatric Eye Disease Investigator Group. Stability of visual acuity improvement following discontinuation Lens Association 9 (1986):95-100. https://doi.org/10.1016/s0141- of amblyopia treatment in children 7 to 12 years old. 7037(86)80034-9 Arch Opthalmol 125(2007):655-9. https://doi.org/10.1001/ 17. Scheiman M, Wick, B. Clinical Management of Binocular archopht.125.5.655 Vision: , Accommodative, and Eye movement Disorders. 3rd Edition. Philadelphia: Lippincott Williams & 33. Holmes JM, et al. Factors associated with recurrence of Wilkins, 2008. 478-495, 525-554. amblyopia on cessation of patching. Ophthalmology 114 (2007):1427-1432. https://doi.org/10.1016/j.ophtha.2006.11.023 18. Greenwald IB. A binocular approach to amblyopia therapy. J Optom Vis Dev 26 (1995):62-67. 34. Pediatric Eye Disease Investigator Group. Effect of a binocular iPad game versus part-time patching in children 19. Kutschke PJ, Scott WE, and Keech RV. Anisometropic aged 5 to 12 with amblyopia: a randomized clinical trial. amblyopia. Ophthalmology 98 (1991):258-63. https://doi. JAMA Ophthalmol 136 (2018):1391-1400. org/10.1016/s0161-6420(91)32307-8

111 Vision Development & Rehabilitation Volume 5, Issue 2 • June 2019 35. Pediatric Eye Disease Investigator Group. Pediatric Eye 51. Garzia RP. Efficacy of vision therapy in amblyopia: a litera­ Disease Investigator Group. A Randomized Trial Of A ture review. Am J Optom Physiol Optics 64 (1987):393-404. Binocular iPad Game Versus Part-Time Patching In Children https://doi.org/10.1097/00006324-198706000-00003 13 To 16 Years Of Age With Amblyopia. Am J Ophthalmol 52. Leyman IR. A comparative study in the treatment of 186 (2018):104-15. https://doi.org/10.1016/j.ajo.2017.11.017 amblyopia. Am Orthop J. 28 (1978):95-9. https://doi.org/10.1 36. Gao TY, et al. Effectiveness of a binocular video game 080/0065955x.1978.11982464 vs placebo video game for improving visual functions 53. Callahan WP, Berry D. The value of visual stimulation during in older children, teenagers, and adults with amblyopia. contact and direct occlusion. Am Orthopt J 18 (1968):73-4. JAMA Ophthalmol 133 (2015):172-81. 54. Von Noorden GK., et al. Home therapy for amblyopia. 37. Hess RF, Mansouri B, and Thompson B. A new binocular Am Orthopt J 20 (1970):46-50. https://doi.org/10.1080/006595 approach to the treatment of amblyopia in adults well 5x.1970.11982261 beyond the of visual development. Restor Neurol Neurosci 28 (2010):793-802. 55. Pediatric Eye Disease Investigator Group. A randomized trial to evaluate 2 hours of daily patching for strabismic 38. Knox PJ, et al. An exploratory study: prolonged periods of and anisometropic amblyopia in children. Ophthalmology binocular stimulation can provide an effective treatment 113 (2006):904-912. https://doi.org/10.1016/j.ophtha.2006.01.069 for childhood amblyopia. Invest Ophthalmol Vis Sci 53 56. Pediatric Eye Disease Investigator Group. Feasibility of a (2012):817-24. https://doi.org/10.1167/iovs.11-8219 clinical trial of vision therapy for treatment of amblyopia. 39. Li J, et al. Dichoptic training enables the adult amblyopic Optom Vis Sci 90 (2013):475-481. https://doi.org/10.1097/ to learn. Curr Biol 23 (2013):R308-9. https://doi. opx.0b013e31828def04 org/10.1016/j.cub.2013.01.059 57. Pediatric Eye Disease Investigator Group. Randomized 40. Li SL, et al. A binocular iPad treatment for amblyopic trial of treatment of amblyopia in children aged 7 to 17 children. Eye (Lond) 28 (2014):1246-53. https://doi.org/10.1038/ years. Arch Opthalmol 123 (2005):437-447. https://doi. eye.2014.165 org/10.1001/archopht.123.4.437 41. Birch EE, et al. Binocular iPad treatment for amblyopia 58. Lithander J, Sjostrand, J. Anisometropic and strabismic in preschool children. J AAPOS 19 (2015):6-11. https://doi. amblyopia in the age group 2 years and above: a org/10.1016/j.jaapos.2014.09.009 prospective study of the results of treatment. Br J 42. Herbison N, et al. Randomised controlled trial of video Ophthalmol 75 (1991):111-6. https://doi.org/10.1136/bjo.75.2.111 clips and interactive games to improve vision in children 59. Wick B., et al. Anisometropic amblyopia: is the patient ever with amblyopia using the I-BiT system. Br J Ophthalmol 100 too old to treat? Optom Vis Sci 69 (1992):566-78. https://doi. (2016):1511-16. https://doi.org/10.1136/bjophthalmol-2015-307798 org/10.1097/00006324-199211000-00006 43. Bossi M., et al. Binocular therapy for childhood amblyopia 60. Kivlin J, Flynn J. Therapy of Anisometropic Amblyopia. J improves vision without breaking interocular suppression. Pediatr Ophthalmol Strabismus 18 (1981):47-56 Invest Ophthalmol Vis Sci 58 (2017):3031-43. https://doi. 61. Birnbaum MH., et al. Success in amblyopia therapy as a func­ org/10.1167/iovs.16-20913 tion of age: a literature survey. Am J Optom Physiol Opt 54 44. Portela-Camino JA., et al. A random dot computer video (1977):269-75. https://doi.org/10.1097/00006324-197705000-00001 game improves stereopsis Optom Vis Sci 95 (2018):523-5. 62. Younger age associated with greater treatment response https://doi.org/10.1097/opx.0000000000001222 in children with amblyopia. ScienceDaily. JAMA and 45. Vera-Diaz FA., et al. A flicker therapy for the treatment of Archives Journals, 12 July 2001. Web. 20 Feb. 2014. amblyopia Vis Dev Rehab 2 (2016):105-14. 46. London R, , JL. Diagnosis Amblyopia: Emphasis on CORRESPONDING Nonacuity Factors. Problems in : Amblyopia. AUTHOR BIOGRAPHY: Rutstein, RP. Philadelphia: J.B. Lippincott Company, 1991. Sung Hee (Kelly) Lee, OD, FAAO 47. Abrahamsson M, Sjostrand J. Contrast sensitivity and Dr. Kelly Lee earned both her BSc acuity relationship in strabismic and anisometropic degree in science and Doctor of amblyopia. Br J Ophthalmol 72 (1988):44-9. https://doi. Optometry degree from the University org/10.1136/bjo.72.1.44 of Waterloo in Canada. She completed 48. Cohen AH. Monocular fixation in a binocular field. J Am her residency in Vision Therapy, Optom Assoc 52 (1981):801-6. Rehabilitation, and Pediatrics at Pacific 49. Pediatric Eye Disease Investigator Group. Stereoacuity University College of Optometry. in children with anisometropic amblyopia. J AAPOS 15 Dr. Lee is a Fellow of the American Academy of Optometry (2011):455-461. (FAAO). She was previously an adjunct faculty member at 50. Wick, B., et al. Anisometropic amblyopia: Is the patient the School of Optometry and Vision Science, University of ever too old to treat? Optom Vis Sci 69 (1992):866-78. Waterloo, and is now fully committed to a private vision https://doi.org/10.1097/00006324-199211000-00006 therapy clinic in the Toronto area.

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